I think we are on the same page, but just want to make sure. I wasn't 100% clear in my initial post. Be sure to take off the siding on a side opposite from the prevailing winds.
If you have to wear a mask in there, then I'd be concerned about the chickens without masks having to breath that air. What is the dust from? Dirt? Hemp? Something else?
I'd think about a much larger opening for ventilation. The prevailing winds likely only come in from one or two sides...